High silicon steel plate has been used for electromagnetic steel. It is known that with this kind of steel, the higher is the Si content, the lower is the hysteresis loss, and at an Si of 6.5 wt %, the magnetic strain is 0. Also Maximum magnetic permeability is exhibited.
For producing high silicon steel strip, several methods have been used; a rolling method, a direct casting method and a siliconizing method. The rolling method is generally not used when Si content exceeds about 4 wt %, because with higher Si content, cold working becomes difficult. The direct casting method, that is, strip casting does not suffer from this same difficulty associated with the rolling method, but deformation is a problem, making it especially difficult to produce high silicon steel strip of high quality.
On the other hand, the siliconizing method begins with a molten low silicon steel, rolls the steel into a thin strip, and applies Si to the surface thereof in such a way that it permeates the entire strip thereby avoiding both the problem workability and deformation.
Siliconizing methods have been proposed by Itsumi and Abe, and studied in detail by Mitsuya and Onishi. All of these proposed methods require appreciable time for siliconization, more than 30 minutes, and are therefore not generally useful for a continuous production line. Also, since the treatment temperature is very high, as much as 1230.degree. C., the shape of thin steel sheets after siliconization is very bad; in addition, there is danger that the edge parts may melt owing to overheating because the treatment temperature is too high. Thus, one cannot plan on stable running of the strips in a continuous line environment.
The present invention seeks to avoid these shortcomings in the prior art using the siliconizing method to efficiently produce stable high silicon steel strip of high quality in a continuous process.